Why android os using data while I'm connected to wifi on my galaxy s6?

[TheSamsungGuy]

Sometimes at random, the 4G/LTE symbol appears at the top even though it shouldn't while I'm connected to my home's wifi. Then, when I check my data usage, the android os has used data during that time the symbol was there. Anybody have a clue how to stop this?

 

[kmf1]

Do you have Avoid bad WiFi connections enabled in Settings/WiFi/3 dots/Advanced? This can create data consumption if the phone thinks that it has a poor wifi connection. I have that turned off.

 

[lucianus_luciferus]

Also turn off download booster in settings, more connection settings

 

[buksiej]

You could always just switch your data off when connected to the wifi. It takes more effort to switch in-between them when you're going in and out of the house but this way you are guaranteed not to have your data used up.